With the popularization of a dense wavelength division multiplexing (DWDM) system of a standard single mode fiber, and the development trend towards high speed, long distance, non-relay and dense channels, the wavelength division multiplexing technology is developed rapidly; and the working wavelength band is rapidly expanded, and the wavelength is diversified rapidly.
At the wavelength of 1310 nm, a long-haul fiber constructed based on G.652 fibers has minimum dispersion, but has significant attenuation, while at the waveband of 1550 nm, the long-haul fiber has lowest attenuation (about 0.20 dB/km). Therefore, people are eager to utilize the wavelength window of 1550 nm. The successful development and practice of an erbium-doped optical fiber amplifier (EDFA) working at the waveband of 1550 nm further eliminate the limitation of the attenuation on a communications system, which makes the waveband of 1550 nm a preferential window for a large-capacity and long-distance optical wave system. At the waveband of 1550 nm, a commercial single mode fiber and a DCF thereof at present have the following dispersion features: a dispersion coefficient of a non-dispersion shifted single mode fiber (G.652C/D, ITU-T standard) is about 17 ps/nm-km, and a dispersion slope thereof is about 0.058 ps/nm2-km; therefore, a relative dispersion slope (RDS) required by the non-dispersion shifted single mode fiber is about 0.0036 nm−1.
In order to solve the upgrade and capacity expansion problems of a communications network formed of 1310 nm zero-dispersion standard single mode fibers at the waveband of 1550 nm, dispersion compensation technologies are widely used all over the world to solve the link dispersion. At present, a dispersion compensation fiber (DCF) technology is largely commercialized to compensate the dispersion and dispersion slope of a communication link fiber at the same time. Compared with other dispersion compensation technologies such as fiber grating dispersion compensation and electronic dispersion compensation, this technology is more reliable and more mature.
The DCF changes transmission parameters of an optic signal in the fiber by adjusting a waveguide structure of the fiber, so that the core of the fiber has a great refractive index, thereby achieving great negative dispersion value and dispersion slope.
In practical applications, the DCF is made into a dispersion compensation module and connected into the communication link. At this time, the splice loss between the DCF and the standard communication fiber becomes an important impact factor of insertion loss. Therefore, the splice performance of the DCF is a key parameter. A DCF with applicability not only needs to have appropriate optical performance and transmission performance, but also needs to have excellent splice performance, which means a low splice loss and an efficient and stable splice process. The splice performance becomes an important factor that influences the DCF cost and performance. A lower splice loss guarantees better performance of the module, and a faster and more efficient splice procedure reduces the splice cost.
In published patent documents, some product and method examples for improving the DCF splice performance are provided. For a 1550 nm light source, a mode field diameter of the DCF is about 5 μm, while a mode field diameter of a standard communication fiber is 10.5 μm. As a result of such difference in the mode field (mode field mismatching), leakage easily occurs when optical power is introduced from a large mode field to a small mode field. The prior art relates to employing a complex splice process to disperse the DCF fiber core near the end face interface of the splice fiber, so as to distribute the DCF mode field nearby into a conical transition area; a “chimney effect” of the area helps reduce the optical power loss caused by mode field mismatching, thereby reducing the splice loss.
The prior art also relates to a method of using a “bridge fiber” as a bridge to connect the DCF and standard single mode fiber. The bridge fiber is a kind of special fiber with a structure similar to the DCF, while a doping concentration of each layer is lower than that of the DCF. Two ends of the bridge fiber are respectively spliced with the DCF and the standard single mode fiber by using different splice processes. The end of the bridge fiber, which is connected with the DCF, uses low splice power and short splice time so as to reduce core area element dispersion and mode field mismatching; the other end of the bridge fiber, which is connected with the single mode fiber, uses high splice power and long splice time so that the fiber core of the bridge fiber is dispersed, thereby achieving mode field matching.
The U.S. Pat. No. 6,603,914 introduces a composition structure and a manufacturing method of a DCF, but does not relate to the splice method and the optical transmission performance of the DCF. The U.S. Pat. No. 6,543,942 describes a method for connecting a DCF and a standard single mode fiber by using a bridge fiber, which reduces the splice loss, but the patent does not correspondingly disclose the optical transmission performance of the DCF; in addition, the method involves a complex process, takes a long time, has low splice efficiency, and thus is not practical. No Chinese patent relating to the splice method for a DCF is available.
The documents described above relate to various methods for improving the splice performance of the DCF and standard single mode fiber as well as corresponding DCF products, but no method capable of improving the splice performance while having excellent optical transmission performance and a spice method thereof have been reported.
Therefore, a heretofore unaddressed need exists in the art to address the aforementioned deficiencies and inadequacies.